CN113557089A - Adhesive composition for enhancing adhesion of catalyst washcoat - Google Patents

Abstract

The present disclosure provides binder compositions formed from a plurality of binder materials having different average particles that can be used to improve the adhesion of a washcoat on a substrate. The improvement in adhesion may be related to increasing the adhesive concentration without a significant or substantial increase in the associated viscosity. Such binder compositions may include a first binder material formed from a plurality of particles having a first average particle size and a second binder material formed from a plurality of particles having a second average particle size, wherein the ratio of the first average particle size to the second average particle size is about 2 or greater. The present disclosure further provides catalyst compositions, catalyst articles, and emissions systems incorporating the binder composition.

Description

Adhesive composition for enhancing adhesion of catalyst washcoat

Cross Reference to Related Applications

This application claims priority in its entirety from U.S. provisional application No. 62/818378 filed on 3/14/2019 and european application No. 19175283.1 filed on 5/20/2019.

Technical Field

The present invention relates generally to the field of compositions useful for forming catalysts, and to the field of catalytic articles comprising such compositions and methods of making and using such catalytic articles.

Background

With timeTransition of Nitrogen Oxides (NO)_x) The harmful components cause atmospheric pollution. Such as exhaust gases from internal combustion engines (e.g. in cars and trucks), combustion plants (e.g. power stations heated by natural gas, oil or coal) and nitric acid production plants, contain NO_x。

Various treatment methods have been used to treat NO-containing materials_xTo reduce atmospheric pollution. One treatment involves the catalytic reduction of nitrogen oxides. There are two methods: (1) a non-selective reduction method in which carbon monoxide, hydrogen or a lower hydrocarbon is used as a reducing agent; and (2) a selective reduction process in which ammonia or an ammonia precursor is used as a reducing agent. In selective reduction processes, a high degree of nitrogen oxide removal can be achieved with a small amount of reducing agent.

Catalytic articles useful for providing such catalytic reduction are typically prepared by applying the catalyst material to a substrate, typically in the form of a washcoat composition. To ensure durability of the catalytic article, it is beneficial for the washcoat composition to remain substantially adhered to the substrate with minimal loss throughout the useful life of the catalytic article.

To enhance the bond strength between the catalyst washcoat and the substrate, one or more binders may be added to the washcoat composition. However, improving the adhesion of the washcoat to the substrate by using a binder can be problematic. Increasing the total binder content in the washcoat composition can significantly increase the overall viscosity of the composition, which in turn can prevent the washcoat composition from being uniformly coated along the substrate. Non-uniformity of application can then lead to loss of the washcoat over time. On the other hand, reducing the total binder content in the washcoat composition may undesirably reduce the adhesion strength of the washcoat to the substrate. The reduction in bond strength then results in loss of the washcoat over time. Thus, it may be difficult to obtain the appropriate binder content needed to achieve the appropriate loss profile, and there remains a need in the art for additional binder compositions for forming catalytic articles.

Disclosure of Invention

The present disclosure relates to compositions useful for forming catalyst articles. The composition comprises a plurality of binders having different average particle sizes, the plurality of binders being present in a defined ratio. The compositions comprising the plurality of binders are useful for enhancing the adhesion of catalyst washcoat on a substrate. The combination of binders specifically described herein can increase the total binder content that can be utilized without an undesirable increase in washcoat viscosity. Also, the combination of multiple binders may improve the viscoelastic behavior of the washcoat with which it adheres to the substrate.

In one or more embodiments, the present disclosure may relate to an adhesive composition including a plurality of adhesive materials having defined ratios and sizes. For example, the adhesive composition may include: a first binder material formed from a plurality of particles having a first average particle size; and a second binder material formed from a plurality of particles having a second average particle size; wherein the ratio of the first average particle size to the second average particle size is about 2 or greater. In further embodiments, the adhesive composition may be defined with respect to one or more of the following statements, which may be combined in any number and order.

The first adhesive material and the second adhesive material are independently selected from the group consisting of: alumina-containing materials, silica-containing materials, zirconia-containing materials, ceria-containing materials, lanthanum oxide-containing materials, yttria-containing materials, and combinations thereof.

The first binder material is an alumina-containing material and the second binder material is a zirconia-containing material.

The adhesive composition further includes a third adhesive material formed from a plurality of particles having a third average particle size, wherein the ratio of the third average particle size to the first average particle size is about 2 or greater, or wherein the ratio of the second average particle size to the third average particle size is about 2 or greater.

The adhesive composition further includes a third adhesive material formed from a plurality of particles having a third average particle size, wherein a ratio of the first average particle size to the third average particle size is about 2 or greater.

The first average particle size is from about 50nm to about 1000 nm.

The second average particle size is from about 10nm to about 500 nm.

The first binder material and the second binder material are present in a concentration ratio of about 0.01 to about 0.5.

One or both of the first binder material and the second binder material are catalytic.

In one or more embodiments, the present disclosure may be directed to a washcoat slurry. For example, such washcoat slurries may include: a liquid medium; and an adhesive composition as otherwise described herein. In further embodiments, the washcoat slurry may be defined with respect to one or more of the following statements, which may be combined in any number and order.

The adhesive composition is at a level of from about 0.01 to about 1.0g/in³And wherein the washcoat slurry is present in about 300s^-1The viscosity of (a) is about 100cP or less.

The washcoat slurry was in about 300s^-1The viscosity of (a) is about 50cP or less.

The washcoat slurry further includes a catalyst material.

In one or more embodiments, the present disclosure may be directed to a catalyst article. For example, a catalyst article can include a catalyst substrate having a plurality of channels adapted for gas flow, a wall surface of each channel adhered to a catalytic coating comprising an adhesive composition as otherwise described herein. In further embodiments, the catalyst article may be defined with respect to one or more of the following statements, which may be combined in any number and order.

The catalytic coating includes a catalyst material in combination with the binder composition.

The catalyst substrate is a honeycomb comprising a wall flow filter substrate or a flow-through substrate.

The catalytic coating is applied at a rate of at least about 1.0g/in³Is present on the substrate.

The catalyst substrate comprises a first coating layer of the catalytic coating and comprises a second coating layer having a different overall composition overlying at least a portion of the first coating layer of the catalytic coating.

One or both of the following conditions may be satisfied: the first binder material is present in an amount of about 0.1 wt% to about 5 wt% of the total dry gain of the first coating of the catalytic coating; the second binder material is present in an amount of about 7 wt% to about 20 wt% of the total dry gain of the first coating of the catalytic coating.

In one or more embodiments, the present disclosure may be directed to an emission treatment system for treating an exhaust gas stream. For example, an emissions treatment system may include: an engine that produces an exhaust gas stream; and a catalyst article as otherwise described herein positioned downstream of the engine and in fluid communication with the exhaust stream.

Drawings

For the purpose of providing an understanding of embodiments of the invention, reference is made to the accompanying drawings, which are not necessarily drawn to scale, and in which reference numerals refer to components of exemplary embodiments of the invention. The drawings are exemplary only, and should not be construed as limiting the invention.

FIG. 1 is a perspective view of a honeycomb substrate carrier that may include a washcoat composition according to the present invention;

FIG. 2 is a partial cross-sectional view enlarged relative to FIG. 1 and taken in a plane parallel to an end face of the substrate carrier of FIG. 1, the substrate carrier representing a monolithic flow-through substrate, the figure showing an enlarged view of the plurality of gas flow channels shown in FIG. 1;

FIG. 3 is an enlarged fragmentary cross-sectional view relative to FIG. 1, wherein the honeycomb substrate support of FIG. 1 represents a wall-flow filter substrate monolith;

FIG. 4 is a schematic view of an emissions treatment system in which a washcoat composition of the present invention is utilized;

FIG. 5 is a schematic view of an emissions treatment system wherein a washcoat composition of the present invention is used to form side-by-side coatings;

FIG. 6 is a schematic view of an emissions treatment system in which a washcoat composition of the present invention is utilized;

FIG. 7 is a schematic view of an emission treatment system in which the washcoat composition of the present invention is utilized and which includes an optional particulate filter;

FIG. 8 is a contour plot showing viscosity (cP) of an example washcoat composition based on relative loadings of particles of a first binder and particles of a second binder, where the second binder (y-axis) and the first binder (x-axis) are normalized loadings relative to a baseline, according to an embodiment of the disclosure; and is

Fig. 9 is a contour plot showing percent loss of an example washcoat based on relative loading of particles of a first binder and particles of a second binder used in preparing a composition for forming the washcoat in accordance with an embodiment of the present disclosure, where the second binder (y-axis) and the first binder (x-axis) are loading amounts normalized to a baseline.

Detailed Description

The present disclosure will now be described more fully hereinafter. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

As used in this specification and the claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

The term "about" is used in this specification to describe and account for small fluctuations. For example, the term "about" may refer to less than or equal to ± 5%, such as less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.2%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%. All numerical values herein are modified by the term "about," whether or not explicitly indicated. A value modified by the term "about" naturally encompasses the particular value.

The present disclosure generally provides compositions that may include a variety of binders. The composition may comprise one or more catalysts, and the one or more catalysts may comprise one or more binders of the plurality of binders or may be present in a form other than a binder. The present disclosure further provides washcoat compositions, catalyst articles, and catalyst systems including such catalyst articles. In one or more embodiments, such articles and systems may include a three-way conversion (TWC) catalyst composition, a Diesel Oxidation Catalyst (DOC), an SCR, and/or an ammonia oxidation catalyst (AMOx). As such, in certain embodiments, the present compositions may be provided as a coating or coatings on a flow-through substrate, as otherwise described herein. In further embodiments, the present compositions may be provided as a coating or coatings on a wall flow substrate, as further described herein.

For the purposes of this application, the following terms shall have the respective meanings set forth below.

As used herein, the term "catalyst" or "catalyst composition" refers to a material that promotes a reaction.

As used herein, the terms "upstream" and "downstream" refer to the relative direction of flow from the engine to the tailpipe according to the engine exhaust gas flow, with the engine at an upstream location and the tailpipe and any pollution abatement articles (e.g., filters and catalysts) downstream of the engine.

As used herein, the term "flow" broadly refers to any combination of flowing gases that may contain solid or liquid particulate matter. The term "gas stream" or "exhaust gas stream" means a gaseous component stream (e.g., the exhaust of a lean-burn engine) that may contain entrained non-gaseous components, such as liquid droplets, solid particulates, and the like. The exhaust stream of a lean burn engine typically further includes products of combustion, products of incomplete combustion, oxides of nitrogen, combustible and/or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen.

As used herein, the term "substrate" refers to a monolith having disposed thereon a catalyst composition, typically in the form of a washcoat containing a plurality of particles having the catalyst composition thereon. The washcoat is formed by preparing a slurry containing particles at a solids content (e.g., 10-80% by weight) in a liquid vehicle, which is then applied to a substrate and dried to provide a washcoat layer.

As used herein, the term "washcoat" is generally used in the art to mean a thin adherent coating of catalytic or other material applied to a substrate material (e.g., a honeycomb-type support member) that is sufficiently porous to allow the passage of the treated gas stream.

As used herein, the term "catalyst article" refers to an element used to promote a desired reaction. For example, the catalyst article may include a washcoat containing the catalytic composition on a substrate.

The term "decrease" means a decrease in the amount, and "decrease" means a decrease in the amount caused by any means.

In one or more embodiments, the present disclosure provides an adhesive composition. The adhesive composition is formed from a plurality of different adhesive materials. As such, the adhesive composition may include at least a first adhesive material and a second adhesive material. In further embodiments, additional adhesive materials may also be used, and such adhesive materials may be referred to as, for example, a third adhesive material, a fourth adhesive material, and so forth. The adhesive material may differ in one or more respects. For example, the binder materials may differ in the chemical nature of the materials. In other examples, the binder materials may differ in one or more physical properties such as the average size of the particles forming the binder material. In particular embodiments, the binder materials may differ in both chemical structure and one or more physical properties.

In some embodiments, it has been found that particularly desirable effects may be obtained when the binder composition according to the present disclosure includes at least a first binder material formed from a plurality of particles having a first average particle size and a second binder material formed from a plurality of particles having a second average particle size. In embodiments where a third binder material, a fourth binder material, or even more binder materials are used, the third binder material may be formed from a plurality of particles having a third average particle size, the fourth binder material may be formed from a plurality of particles having a fourth average particle size, and so on.

As used herein, the binder particle size may be a D50 particle size, or the binder particle size may be an average particle size. The term "average particle size" is defined as the sum of the particle sizes of all particles measured divided by the total number of particles. The granularity may be calculated using any suitable means in the art. For example, particle size may be measured using laser diffraction, dynamic light scattering (or photon correlation spectroscopy), sedimentation, image analysis, sonography, or any other art-recognized method may be used. The particle size of the adhesive component can be measured using a CILAS1064 laser particle size analyzer according to the liquid mode method recommended by the manufacturer in a measurement range of 0.04 microns to 500 microns. For particles <40nm, particle size can be measured using a Malvern Zetasizer Pro, a high performance two angle particle and molecular size analyzer that is used to enhance the detection of aggregates and the measurement of small or dilute samples and very low or very high concentration samples using dynamic light scattering, using 'NIBS' optics.

The material forming the binder particles may vary depending on its particular intended use. For example, to prepare a catalyst article, it may be desirable to utilize a binder material that also exhibits catalyst activity. Thus, in some embodiments, one or more binder materials used in the binder composition may be catalyst materials or may otherwise provide a functional effect. Also, the binder material used may be particularly suitable for improving the adhesion of a particular catalyst material to a substrate. In some embodiments, rare earth metal oxides may be used as the binder material. In example embodiments, the first and second adhesive materials (and optionally the third adhesive material or even further adhesive materials) may be independently selected from the group consisting of: alumina-containing materials, silica-containing materials, zirconia-containing materials, ceria-containing materials, lanthanum oxide-containing materials, yttria-containing materials, and combinations thereof. In further example embodiments, the binder material used in the compositions of the present disclosure may comprise a binder formed of ceria, zirconia, yttria, lanthana, and combinations thereof.

In one embodiment, the first binder material is an alumina-containing material and the second binder material is a zirconia-containing material. In one embodiment, the adhesive composition comprises: a first binder material formed from a plurality of particles having a first average particle size; and a second binder material formed from a plurality of particles having a second average particle size; wherein the ratio of the first average particle size to the second average particle size is about 2 or greater, wherein the first binder material is an alumina-containing material and the second binder material is a zirconia-containing material. In another embodiment, an adhesive composition includes: a first binder material formed from a plurality of particles having a first average particle size; and a second binder material formed from a plurality of particles having a second average particle size; wherein the ratio of the first average particle size to the second average particle size is about 2 or greater, wherein the first binder material is an alumina-containing material and the second binder material is a zirconia-containing material, wherein the first average particle size is from about 50nm to about 1000nm, wherein the second average particle size is from about 10nm to about 500 nm. In yet another embodiment, an adhesive composition comprises: a first binder material formed from a plurality of particles having a first average particle size; and a second binder material formed from a plurality of particles having a second average particle size; wherein the ratio of the first average particle size to the second average particle size is about 2 or greater, wherein the first binder material is an alumina-containing material and the second binder material is a zirconia-containing material, wherein the first average particle size is about 50nm to about 1000nm, wherein the second average particle size is about 10nm to about 500nm, wherein the first binder material and the second binder material are present in a concentration ratio of about 0.01 to about 0.5.

In some embodiments, the binder materials used herein are combined in a particular ratio based on the average particle size of the various binder materials. Unless otherwise indicated herein, the terms "first," "second," "third," and the like, in relation to various adhesive materials, are used for clarity only, and it is to be understood that the descriptions for "first adhesive material" and "second adhesive material" or another of the various adhesive materials are interchangeable.

As a non-limiting example, the ratio of the average particle size of the first binder material to the average particle size of the second binder material may be about 2 or greater. In other words, the average particle size of the first binder material may be at least 2 times (or more) larger than the average particle size of the second binder material. In further embodiments, the ratio of the first average particle size of the first binder material to the second average particle size of the second binder material may be about 2.5 or greater, about 3 or greater, about 3.5 or greater, about 4 or greater, about 5 or greater, or about 6 or greater. In further example embodiments, the ratio of the first average particle size of the first binder material to the second average particle size of the second binder material may be from about 1 to about 7, from about 1 to about 5, from about 1.5 to about 4, or from about 2 to about 3.

In embodiments where a third binder material is included in the binder composition, the average particle size of the third binder material may be less than the average particle size of the first binder material or may be greater than the average particle size of the third binder material. For example, the ratio of the third average particle size of the third binder material to the first average particle size of the first binder material may be about 1.5 or greater, about 2 or greater, about 2.5 or greater, about 3 or greater, about 4 or greater, or about 5 or greater, such as from about 1 to about 7, from about 1.5 to about 6, or from about 2 to about 5. Further, the ratio of the second average particle size of the second binder material to the third average particle size of the third binder material may be about 1.5 or greater, about 2 or greater, about 2.5 or greater, about 3 or greater, about 4 or greater, or about 5 or greater, such as from about 1 to about 5, from about 1.5 to about 4, or from about 2 to about 3.

In embodiments where a third binder material is included in the binder composition, the average particle size of the third binder material may be less than the average particle size of the first binder material or may be greater than the average particle size of the third binder material. For example, the ratio of the first average particle size of the first binder material to the third average particle size of the third binder material may be about 1.5 or greater, about 2 or greater, about 2.5 or greater, about 3 or greater, about 4 or greater, or about 5 or greater, such as from about 1 to about 7, from about 1.5 to about 6, or from about 2 to about 5.

In some embodiments, the second binder material is a combination of two or more different binder materials each having a certain average particle size. In this embodiment, the second binder material will have an average particle size.

In some embodiments, the average particle size of the at least one binder material may be about 50nm to about 1000nm, about 50nm to about 750nm, about 50nm to about 500nm, about 50nm to about 400nm, about 50nm to 300nm, or about 50nm to about 250 nm. In some embodiments, binder materials having particles within such ranges may be referred to as particles having a relatively large average particle size.

In further embodiments, the average particle size of the at least one binder material may be from about 10nm to about 750nm, from about 10nm to about 500nm, from about 10nm to about 250nm, from about 10nm to about 150nm, from about 15nm to about 150nm, or from about 20nm to about 120 nm. In some embodiments, binder materials having particles within such ranges may be referred to as particles having a relatively small average particle size.

In an example embodiment, the first binder material may be formed from a plurality of particles having a first average size, and the second binder material may be formed from a plurality of particles having a second average size. The first average size may be relatively larger than the second average size, which in turn may be relatively smaller than the first average size. Preferably, the relative sizes of the particles of the first binder material and the particles of the second binder material exhibit the ratios otherwise described herein, independently of the absolute average size of the first binder particles and the absolute average size of the second binder particles.

The third binder material, if present, may be a plurality of particles larger in size than the particles of the first binder material according to the ratios provided above, or may be a plurality of particles smaller in size than the particles of the second binder material according to the ratios provided above. Alternatively, the third binder material, if present, may be a plurality of particles that: the plurality of particles are sized smaller in size than the first binder material particles and larger in size than the second binder material particles, so long as the overall size ratio conforms to the ratios provided above. More specifically, the relative average size of the binder material particles may be according to any one of the following, wherein B1 is the average particle size of the first binder material, B2 is the average particle size of the second binder material, and B3 is the average particle size of the third binder material, and wherein the relative average size is within the ratio ranges otherwise described above: b1> B2; or B2> B1; or B1> B2> B3; or B2> B1> B3; or B2> B3> B1; or B3> B2> B1; or B3> B2> B1; or B1> B3> B2. In a particular embodiment, B1> B2; or B1> B2> B3; or B1> B3> B2.

In addition to the size ratio, in some embodiments, the adhesive composition may be defined according to the concentration ratio of the various adhesive materials present. In particular embodiments, it may be desirable for the binder material having a relatively smaller average particle size to be present in a higher concentration than the binder material having a relatively larger average particle size. For example, the binder material having a relatively larger average particle size and the binder material having a relatively smaller average particle size may be present in a concentration ratio of about 0.01 to about 0.95, about 0.01 to about 0.9, about 0.01 to about 0.8, about 0.02 to about 0.6, about 0.02 to about 0.5, or about 0.3 to about 0.5. Such concentration ratios may be applicable for each additional binder material used having an average particle size that is either relatively larger in turn or relatively smaller in turn.

For a variety of reasons, it may be advantageous to provide a greater concentration of binder material having a relatively smaller average particle size. For example, in some embodiments, having a greater concentration of binder particles with a relatively smaller average particle size may be beneficial to increase the total amount of binder material that may be used. Having a higher total amount of binder material can improve the bond strength between the catalyst washcoat and the catalyst substrate. Also, having a greater concentration of binder particles having a relatively smaller average particle size may be advantageous in maintaining or even reducing the viscosity of a washcoat slurry used to apply a catalyst washcoat to a catalyst substrate. This can be beneficial to improve washcoat uniformity along the length of the substrate and thus avoid catalyst coating areas on the substrate being undesirably thick and/or catalyst coating areas on the substrate being undesirably thick. Thus, an increase in the amount of binder can be achieved using the binder composition of the present disclosure while maintaining or even reducing the binder washcoat viscosity. This can be beneficial to extend the window of operation to enhance adhesion of the catalyst to the substrate.

In further embodiments, the present disclosure may provide a washcoat slurry formed from a liquid medium and a binder composition as further described herein. The liquid medium used in the washcoat slurry may in particular be an aqueous medium, and may in particular be water. The binder material particles forming the two or more binder materials used in the binder composition may be present in the washcoat slurry alone or in combination with a dedicated catalyst material. The phrase "dedicated catalyst material" may refer to a catalyst material that is dedicated to being present as a catalyst in forming a catalyst article and separate from any binder material used in the binder composition, which also functions as a catalyst material.

The binder composition used in the washcoat slurry may be present in a defined amount while maintaining the desired low viscosity. Preferably, the adhesive composition is sufficient to provide a bond between the adhesive and the substrateThe concentration that provides the specified binder loading on the substrate is present in the washcoat slurry. In describing the amount of material (e.g., binder material and/or catalyst material) present in the washcoat slurry, such units may be conveniently used: component weight per unit volume of substrate coated with washcoat. Thus, the units grams per cubic inch ("g/in)³") and grams per cubic foot (" g/ft ")³") is used herein to mean the weight of the components per unit volume of the substrate member (including the volume of the void space of the substrate member). In one or more embodiments, the adhesive composition may be at about 0.01g/in³To about 1.0g/in³About 0.05g/in³To about 0.95g/in³About 0.1g/in³To about 0.9g/in³About 0.15g/in³To about 0.8g/in³Or about 0.2g/in³To about 0.5g/in³Is present in the washcoat slurry. In some embodiments, the binder content may be defined as the concentration by solids content of the entire slurry. For example, it may be desirable for a washcoat composition including a binder composition to include from about 10 wt% to about 60 wt%, from about 15 wt% to about 50 wt%, or from about 20 wt% to about 40 wt% solids, based on the total weight of the washcoat slurry. Preferably, the binder composition comprises from about 1 wt% to about 50 wt%, from about 1.5 wt% to about 35 wt%, or from about 2 wt% to about 20 wt% of the total solids content of the washcoat slurry. Thus, in some embodiments, the binder composition may comprise from about 0.1 wt% to about 12 wt%, from about 0.2 wt% to about 10 wt%, or from about 0.4 wt% to about 8 wt% of the washcoat slurry, based on the total weight of the washcoat slurry. In one embodiment, a washcoat slurry includes: a liquid medium; an adhesive composition as further described herein, wherein the adhesive composition is at about 0.01 to about 1.0g/in³And wherein the washcoat slurry is present in about 300s^-1The viscosity of (a) is about 100cP or less.

The present compositions are particularly advantageous in that increased binder loading can be achieved without undesirably increasing the viscosity of the washcoat slurryAnd (4) degree. For example, a Brookfield viscometer (Brookfield viscometer) can be used at room temperature for about 300s^-1The shear rate of (c) is measured in centipoise (cP). In some embodiments, the viscosity of a washcoat slurry including a binder composition as described herein at the loadings described above may be about 120cP or less, about 100cP or less, about 80cP or less, about 60cP or less, or about 50cP or less (e.g., where the lower limit is greater than one). More specifically, the viscosity of the washcoat slurry as described above may be about 5cP to about 120cP, about 5cP to about 100cP, about 10cP to about 80cP, or about 15cP to about 60 cP.

As noted above, the washcoat slurries described herein may also include one or more catalyst materials in addition to binder materials. In some embodiments, for example, the adhesive composition may be compatible with catalysts suitable for use in, for example, TWC catalysts and/or quaternary transformations (FWC)^TM) One or more of the catalyst compositions are used together. Catalyst compositions having TWC functionality may comprise catalyst compositions effective for Hydrocarbon (HC), carbon monoxide (CO) oxidation and NOx reduction, as required by regulatory agencies and/or automotive manufacturers. In this way, platinum group metal components such as platinum, palladium and rhodium are provided to achieve HC, CO and NOx conversion, and sufficient Oxygen Storage Component (OSC) is provided to achieve sufficient oxygen storage capacity to ensure proper HC, NOx and CO conversion in environments of different a/F (air to fuel) ratios. Sufficient oxygen storage capacity generally means that the catalyst can store and release a minimum amount of oxygen after aging over the full service life as defined by the automotive manufacturer. For example, a useful oxygen storage capacity may be at least 100mg per liter of oxygen (e.g., about 200mg per liter of oxygen after exothermic aging at 1050 ℃ for 80 hours). Examples of suitable oxygen storage components include ceria and praseodymia, and such materials are provided in the form of mixed oxides. For example, ceria can be delivered by a mixed oxide of cerium and zirconium and/or a mixed oxide of cerium, zirconium and neodymium. For example, praseodymium oxide can be delivered by a mixed oxide of praseodymium and zirconium and/or a mixed oxide of praseodymium, cerium, lanthanum, yttrium, zirconium, and neodymium. Suitable TWC catalyst compositions may comprise, for example, those described in U.S. Pat. No. 8,815,189, U.S. Pat. No. 5,those described in national patent No. 9,266,092 and U.S. patent No. 9,981,258, the disclosures of which are incorporated herein by reference.

The binder composition alone (such as when one or more of the binder materials also function as a catalyst material) or in combination with one or more specialized catalyst materials may be used in a catalyst article, where the binder composition (alone or in combination with the catalyst material) may be provided on a catalyst substrate. According to one or more embodiments, the substrate may be composed of any material typically used to prepare automotive catalysts, and will typically comprise a metal or ceramic honeycomb structure. The substrate typically provides a plurality of wall surfaces to which a washcoat containing at least an adhesive composition is applied and adhered, thereby acting as a carrier for the applied composition.

Exemplary metal substrates include heat resistant metals and metal alloys such as titanium and stainless steel and other alloys in which iron is a substantial or major component. Such alloys may comprise one or more of nickel, chromium and/or aluminum, and the total amount of these metals may advantageously constitute at least 15 wt.% of the alloy, e.g., 10-25 wt.% chromium, 3-8 wt.% aluminum and up to 20 wt.% nickel. The alloy may also contain small or trace amounts of one or more other metals, such as manganese, copper, vanadium, titanium, and the like. The surface or metal support may be oxidized at high temperatures (e.g., 1000 ℃ or higher) to form an oxide layer on the substrate surface, thereby improving the corrosion resistance of the alloy and promoting adhesion of the washcoat layer to the metal surface.

The ceramic material used to construct the substrate may comprise any suitable refractory material, for example, cordierite, mullite, cordierite-alpha alumina, silicon carbide, silicon nitride, aluminum titanate, zircon mullite, spodumene, alumina-silica magnesia, zirconium silicate, sillimanite, magnesium silicate, zircon, petalite, alpha alumina, aluminosilicates, and the like.

Any suitable substrate may be employed, such as a monolithic flow-through substrate having a plurality of fine, parallel gas flow channels extending from the inlet to the outlet face of the substrate such that the channels open to fluid flow. The channels, which are essentially straight paths from the inlet to the outlet, are defined by walls that are coated with a catalytic material as a washcoat (e.g., comprising a binder composition) such that the gas flowing through the channels contacts the catalytic material. The flow channels of the monolithic substrate are thin-walled channels that can be of any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, and the like. Such structures may contain from about 60 to about 1200 or more gas inlet openings (i.e., "cells") (cpsi) per square inch of cross-section, more typically about 300 to 600 cpsi. The wall thickness of the flow-through substrate can vary, with a typical range between 0.002 to 0.1 inch. Representative commercially available flow-through substrates are cordierite substrates having 400cpsi wall thickness of 6 mils, or 600cpsi wall thickness of 4 mils. However, it will be understood that the invention is not limited to a particular substrate type, material, or geometry.

In an alternative embodiment, the substrate may be a wall flow substrate, wherein each channel is blocked with a non-porous plug at one end of the substrate body, wherein alternate channels are blocked at opposite end faces. This requires the gas to flow through the porous walls of the wall flow substrate to reach the outlet. Such monolithic substrates may contain up to about 700 or more cpsi, such as about 100 to 400cpsi, and more typically about 200 to about 300 cpsi. The cross-sectional shape of the cells may vary as described above. The wall thickness of the wall flow substrate is typically between 0.002 inches and 0.1 inches. Representative commercially available wall flow substrates are composed of porous cordierite, an example of which is 200cpsi with wall thicknesses of 10 mils or 300cpsi with wall thicknesses of 8 mils, and wall porosity between 45% and 65%. Other ceramic materials such as aluminum titanate, silicon carbide, and silicon nitride are also used as wall flow filter substrates. However, it will be understood that the invention is not limited to a particular substrate type, material, or geometry. It is noted that where the substrate is a wall flow substrate, the catalyst composition (e.g., a TWC catalyst and/or FWC)^TMCatalyst) may penetrate (i.e., partially or partially) into the pore structure of the porous wall in addition to being disposed on the surface of the wallCompletely occluding the pore opening). Fig. 1 and 2 show an exemplary substrate 2 in the form of a flow-through substrate coated with a washcoat composition as described herein. Referring to fig. 1, an exemplary substrate 2 has a cylindrical shape and a cylindrical outer surface 4, an upstream end face 6 and a corresponding downstream end face 8, which is identical to end face 6. The substrate 2 has a plurality of parallel fine gas flow channels 10 formed therein. As seen in fig. 2, the flow channels 10 are formed by walls 12 and extend through the carrier 2 from the upstream end face 6 to the downstream end face 8, the channels 10 being unobstructed to allow fluid (e.g., gas flow) to flow longitudinally through the carrier 2 through its gas flow channels 10. As can be more readily seen in fig. 2, the walls 12 are sized and configured such that the gas flow channels 10 have a substantially regular polygonal shape. As shown, the washcoat composition may be applied in multiple, distinct layers, if desired. In the illustrated embodiment, the washcoat is comprised of a discrete bottom washcoat layer 14 adhered to the wall 12 of the carrier member and a second discrete top washcoat layer 16 coated on the bottom washcoat layer 14. The invention may be practiced with one or more (e.g., 2, 3, or 4) washcoat layers and is not limited to the two-layer embodiment shown.

Fig. 3 shows an exemplary substrate 2 in the form of a wall-flow filter substrate coated with a washcoat composition as described herein. As shown in fig. 3, the exemplary substrate 2 has a plurality of channels 52. The channels are surrounded tubularly by the inner wall 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. Alternate channels are plugged at the inlet end with inlet plugs 58 and at the outlet end with outlet plugs 60 to form an opposing checkerboard pattern at the inlet 54 and outlet 56. The gas flow 62 enters through the unplugged channel inlet 64, is stopped by the outlet plug 60, and diffuses through the trench walls 53 (which are porous) to the outlet side 66. Gas cannot return to the inlet side of the wall due to the inlet plug 58. The porous wall flow filters used in the present invention are catalyzed in that the walls of the element have or contain one or more catalytic materials. The catalytic material may be present on the inlet side of the element walls alone, on the outlet side alone, on both the inlet and outlet sides, or the walls themselves may be filled in whole or in part with the catalytic material. The invention comprises the use of one or more layers of catalytic material within the walls of the element or on the inlet and/or outlet walls of the element.

For example, in one embodiment, a catalytic article includes a catalytic material having multiple layers, where each layer has a different catalyst composition. The bottom layer (e.g., layer 14 of fig. 2) can include a first catalyst composition and the top layer (e.g., layer 16 of fig. 2) can include a second catalyst composition. One or both of the first catalyst composition and the second catalyst composition may comprise an adhesive composition as described herein. It should be understood in fig. 2 that each of the bottom layer 14 and the top layer 16 may extend completely from the front or inlet end of the substrate to the back or outlet end of the substrate.

As a non-limiting example, the catalyst material or catalyst composition used to form the catalyst article herein can include any catalyst commonly used in, for example, automotive catalysts. In some embodiments, catalyst articles according to the present disclosure may comprise an adhesive composition as described herein and be suitable for use as TWC catalysts, FWCs^TMOne or more catalyst compositions of a catalyst, a Diesel Oxidation Catalyst (DOC), a Gasoline Particulate Filter (GPF), a Lean NOx Trap (LNT), an integrated LNT-TWC, and/or an ammonia oxidation (AMOx) catalyst.

In some embodiments, Platinum Group Metals (PGMs) may be used. Specifically, palladium and/or rhodium may be used; however, other PGMs may also (or alternatively) be used. Further, specific PGMs may be specifically excluded from the present disclosure if necessary. When present, the PGM may be present at least about 0.5g/ft³Or at least about 1.0g/ft³At a loading of, for example, about 20g/ft³There is a maximum load amount. Thus, when PGM is present, the PGM may be present at up to about 20g/ft³Is present in an amount. In certain embodiments, the total PGM loading may be about 0.5g/ft³To about 20g/ft³About 1g/ft³To about 10g/ft³Or about 2g/ft³To about 10g/ft³. In certain embodiments, it may be desirable for the catalyst compositions and/or catalysts of the present disclosureThe reagent preparation is substantially free of PGMs. For this reason, a catalyst composition may be "substantially free" of PGMs if it contains less than 0.1 wt.% PGMs or less than 0.01 wt.% PGMs. Likewise, if the catalyst article has a PGM loading of less than 0.1g/ft³Or less than 0.01g/ft³The catalyst article may be "substantially free" of PGM. Preferably, "substantially free" may mean that only trace amounts are present. In some embodiments, the catalyst composition or catalyst article may be completely free of PGMs, if desired.

In one or more embodiments, an ammonia oxidation catalyst (AMOx) may be used. AMOx catalysts are taught, for example, in U.S. publication No. 2011/0271664, the disclosure of which is incorporated herein by reference. The ammonia oxidation (AMOx) catalyst can be a supported noble metal component that can effectively remove ammonia from an exhaust gas stream. The noble metal may comprise ruthenium, rhodium, iridium, palladium, platinum, silver or gold. For example, the noble metal component comprises a physical mixture or a chemically or atomically doped combination of noble metals. For example, the noble metal component comprises platinum. The platinum may be present in an amount of about 0.008% to about 2 wt% based on AMOx catalyst.

In some embodiments, the substrate may be coated with at least two layers contained in separate washcoat slurries in an axially zoned configuration. For example, the same substrate can be coated with one layer of the washcoat slurry and another layer of the washcoat slurry, where each layer is different, e.g., has a different overall composition. The two separate washcoat compositions may comprise separate catalyst compositions and may not substantially overlap. For example, referring to fig. 4, a first washcoat region 102 comprising a washcoat of a first catalyst composition and a second washcoat region 103 comprising a washcoat of a different second catalyst composition may be positioned side-by-side along a length of the substrate 100. The first washcoat region 102 of particular embodiments extends from the front or inlet end 100a of the substrate 100 in a range of about 5% to about 95%, about 5% to about 75%, about 5% to about 50%, or about 10% to about 35% of the length of the substrate 100. The second washcoat region 103 extends from the rear or outlet end 100b of the substrate 100 from about 5% to about 95%, from about 5% to about 75%, from about 5% to about 50%, or from about 10% to about 35% of the total axial length of the substrate 100. The at least two component catalyst compositions in the treatment system according to the present invention may be zoned to the same substrate.

In some embodiments, as shown in fig. 5, the substrate 100 can be coated with a first coating layer 106 extending from the front or inlet end 100a of the substrate 100 to the rear or outlet end 100b of the substrate 100 and a second coating layer 107 applied over the first coating layer 106 proximate the front or inlet end 100a of the substrate 100 and extending only a portion of the length of the substrate 100 (i.e., terminating before reaching the rear or outlet end 100b of the substrate 100).

In some embodiments, as shown in fig. 6, the substrate 100 may be coated with a first coating layer 115 that is proximate the trailing or outlet end 100b of the substrate 100 and extends only partially along the length of the substrate 100 (i.e., terminates before reaching the leading or inlet end 100a of the substrate 100). The substrate 100 may be coated with a second coating 114. As shown in fig. 6, the second coating layer 114 extends from the front or inlet end 100a of the substrate 100 to the rear or outlet end 100b of the substrate 100 (and is thus completely coated over the first coating layer 115). It will be appreciated that the above embodiments are provided as examples only, and that further combinations of catalytic coatings are contemplated.

In one or more embodiments, a catalyst article according to the present disclosure can specifically comprise a substrate coated with a first coating layer as a bottom layer and a second coating layer as a top layer, wherein one or both of the first coating layer and the second coating layer comprises the adhesive composition described herein. For example, as described above, the first coating or primer layer may include at least a first binder and a second binder (and optionally a third binder). The second coating or top layer may include an adhesive composition as described herein, but in some embodiments may include less adhesive than is present in the first coating.

In describing the amount of washcoat or catalytic metal component or other components of the composition, it is convenient to use the weight units of the components per unit volume of the catalyst substrate. Accordingly, this paper makesIn grams per cubic inch ("g/in)³") and grams per cubic foot (" g/ft ")³") to mean the weight of the components per volume of substrate (including the volume of void space of the substrate). Other weight per volume units, such as g/L, are sometimes used. The total loading of the catalyst composition on the catalyst substrate (e.g., a monolithic flow-through substrate) is typically from about 0.1 to about 6g/in³And more typically from about 1 to about 5g/in³. It is noted that these weights per unit volume are typically calculated by weighing the catalyst substrate before and after treatment with the catalyst washcoat composition, and since the treatment process involves drying and calcining the catalyst substrate at elevated temperatures, these weights represent a substantially solvent-free catalyst coating, since substantially all of the water of the washcoat slurry has been removed. As such, the foregoing value may represent the dry gain or amount of solids present on the substrate after removal of any solvent or other liquid material present in the original washcoat slurry used to apply the solids to the substrate.

In some embodiments, it may be beneficial to utilize a first binder and a second binder (and optionally additional binders) as described herein in concentrations and ratios for achieving a certain dry gain in one or more coatings, wherein the first binder and the second binder (and any optional additional binders) constitute a desired weight ratio of the total dry gain. For example, in certain embodiments, the weight percent of a first binder having a relatively larger average particle size to dry gain in a given coating can be smaller (e.g., 0 wt% to about 5 wt%, 0 wt% to about 2.5 wt%, about 0.1 wt% to about 5 wt%, about 0.2 wt% to about 4 wt%, or about 0.25 wt% to about 3 wt%), and the weight percent of a second binder having a relatively smaller average particle size to dry gain in the same given coating can be larger (e.g., about 7 wt% to about 20 wt%, about 10 wt% to about 15 wt%) (all of the above weight percentages being based on the total weight of dry gain of the given coating). In further examples, the weight percentage of the first binder having a relatively large average particle size present in the coating may be less than 5 wt%, less than 3 wt%, or less than 2.5 wt%, based on the total weight of the dry gain of the coating, which may include zero or may be defined with a minimum value of at least 0.01 wt%. Additionally or alternatively, the weight percentage of the second binder having a relatively small average particle size present in the coating can be greater than 7 wt.%, greater than 8 wt.%, greater than 9 wt.%, or greater than 10 wt.% (e.g., up to a maximum of about 25 wt.% or about 20 wt.%), based on the total weight of the dry gain of the coating.

The catalyst material may be milled to enhance mixing of the catalyst particles and to form a homogeneous material. Milling may be accomplished in a ball mill, continuous mill, or other similar device. In one embodiment, the milled catalyst material is characterized by a D90 particle size of about 5 to about 40 microns, preferably 5 to about 30 microns, more preferably about 5 to about 10 microns. D90 is defined as the particle size at which 90% of the particles have a finer particle size.

Washcoat slurries comprising binder materials alone or in combination with one or more specialized catalyst materials can be coated onto catalyst substrates using washcoat techniques known in the art. In one embodiment, the catalyst substrate is dip coated one or more times in the slurry or otherwise coated with the slurry. Thereafter, the coated substrate is dried at elevated temperatures (e.g., 100 ℃ C. and 150 ℃ C.) for a period of time (e.g., about 10 minutes to about 3 hours), and then calcined by heating (e.g., below 700 ℃ C.), typically for about 10 minutes to about 8 hours.

The temperature during calcination of the coated catalyst substrate is less than about 700 ℃. In some embodiments, the calcination temperature is in the range of about 300 ℃ to about 700 ℃, about 300 ℃ to about 500 ℃, about 350 ℃ to about 500 ℃, about 400 ℃ to about 500 ℃, or about 450 ℃ to about 500 ℃ for a period of time. In some embodiments, the calcination temperature is less than about 700 ℃, about 600 ℃, about 500 ℃, about 450 ℃, about 400 ℃, or about 350 ℃, with the lower limit being 300 ℃. In some embodiments, the calcination time period ranges from about 10 minutes to about 8 hours, from about 1 hour to about 6 hours, or from 3 hours to about 6 hours (i.e., less than 8 hours, 7 hours, 6 hours, 5 hours, 4 hours, 3 hours, 2 hours, or 1 hour, with the lower limit being about 10 minutes).

After drying and calcining, the final washcoat coating can be considered to be substantially solvent-free. After calcination, the catalyst loading can be determined by calculating the difference between the coated weight and the uncoated weight of the substrate. As will be apparent to those skilled in the art, the catalyst loading can be modified by altering the slurry rheology. In addition, the coating/drying/calcining process to produce the washcoat can be repeated as necessary to build the coating to a desired loading level or thickness, meaning that more than one washcoat layer may be applied. For example, in some embodiments, the catalyst composition may be applied as a single layer or as multiple layers. In one embodiment, the catalyst material in combination with the binder material described herein may be applied in a single layer (e.g., only layer 14 of fig. 2). In one embodiment, the catalyst material in combination with the adhesive material described herein may be applied in multiple layers (e.g., layers 14 and 16 of fig. 2).

In some embodiments, the calcined coated substrate is aged. Aging can be carried out under a variety of conditions, as used herein, "aging" is understood to encompass a range of conditions (e.g., temperature, time, and atmosphere). Exemplary aging protocols involve treating the calcined coated substrate in 10% steam at a temperature of 650 ℃ for about 50 hours, in 10% steam at a temperature of 750 ℃ for about 5 hours, or in 10% steam at a temperature of 800 ℃ for about 16 hours. However, these schemes are not limiting, and the temperature can be lower or higher (e.g., including, but not limited to, 400 ℃ and higher temperatures, such as 400 ℃ to 900 ℃, 600 ℃ to 900 ℃, or 650 ℃ to 900 ℃); the time may be shorter or longer (e.g., including, but not limited to, a time of about 1 hour to about 50 hours or about 2 hours to about 25 hours); and the atmosphere may be modified (e.g., where different amounts of steam and/or other components are present).

The present disclosure also provides an emissions treatment system incorporating one or more of the compositions described herein. The binder compositions described herein (alone or in combination with one or more specialized catalyst materials) may be used in an integrated emission treatment system that includes one or more additional components for treating exhaust emissions, such as exhaust emissions from gasoline engines.

An exemplary emissions treatment system is illustrated in FIG. 7, which depicts a schematic of the emissions treatment system 32. As shown, the exhaust flow containing gaseous pollutants is delivered from the engine 34 through an exhaust conduit 36 to a TWC catalyst assembly 38 and then in a conduit 40 to a particulate filter assembly 42, which is also optionally coated with TWC. One or both of the TWC catalyst assembly 38 and the particulate filter assembly 42 may include an adhesive composition as described herein.

Exemplary embodiments are as follows.

1. An adhesive composition, comprising:

a first binder material formed from a plurality of particles having a first average particle size; and

a second binder material formed from a plurality of particles having a second average particle size;

wherein the ratio of the first average particle size to the second average particle size is about 2 or greater.

2. The adhesive composition of embodiment 1, wherein the first adhesive material and the second adhesive material are independently selected from the group consisting of: alumina-containing materials, silica-containing materials, zirconia-containing materials, ceria-containing materials, lanthanum oxide-containing materials, yttria-containing materials, and combinations thereof.

3. The binder composition of any one of embodiments 1-2, wherein the first binder material is an alumina-containing material and the second binder material is a zirconia-containing material.

4. The adhesive composition of any one of embodiments 1-3, further comprising a third adhesive material formed from a plurality of particles having a third average particle size, wherein the ratio of the third average particle size to the first average particle size is about 2 or greater, or wherein the ratio of the second average particle size to the third average particle size is about 2 or greater.

The adhesive composition of any one of embodiments 1-4, further comprising a third adhesive material formed from a plurality of particles having a third average particle size, wherein the ratio of the first average particle size to the third average particle size is about 2 or greater.

5. The adhesive composition of any one of embodiments 1-4 a, wherein the first average particle size is from about 50nm to about 1000 nm.

6. The adhesive composition of any one of embodiments 1-5 wherein the second average particle size is from about 10nm to about 500 nm.

7. The adhesive composition of any one of embodiments 1-6 wherein the first adhesive material and the second adhesive material are present in a concentration ratio of about 0.01 to about 0.5.

8. The binder composition of any one of embodiments 1-7, wherein one or both of the first binder material and the second binder material are catalytic.

9. A washcoat slurry comprising:

a liquid medium;

the adhesive composition of any one of embodiments 1-8.

10. The washcoat slurry of embodiment 9, wherein the binder composition is at about 0.01 to about 1.0g/in³And wherein the washcoat slurry is present in about 300s^-1The viscosity of (a) is about 100cP or less.

11. The washcoat slurry of any of embodiments 9-10, wherein the washcoat slurry is in about 300s^-1The viscosity of (a) is about 50cP or less.

12. The washcoat slurry of any of embodiments 9-11, further comprising a catalyst material.

13. A catalyst article comprising a catalyst substrate having a plurality of channels adapted for gas flow, a wall surface of each channel adhered to a catalytic coating comprising the adhesive composition of any of embodiments 1-8.

14. The catalyst article of embodiment 13, wherein the catalytic coating comprises a catalyst material in combination with the binder composition.

15. The catalyst article of any one of embodiments 13 to 14, wherein the catalyst substrate is a honeycomb comprising a wall-flow filter substrate or a flow-through substrate.

16. The catalyst article of any one of embodiments 13 to 15, wherein the catalytic coating is at least about 1.0g/in³Is present on the substrate.

17. The catalyst article of any one of embodiments 13 to 16, wherein the catalyst substrate comprises a first coating layer of the catalytic coating and comprises a second coating layer having a different overall composition that overlies at least a portion of the first coating layer of the catalytic coating.

18. The catalyst article according to any one of embodiments 13 to 17, wherein one or both of the following conditions are satisfied:

the first binder material is present in an amount of about 0.1 wt% to about 5 wt% of the total dry gain of the first coating of the catalytic coating;

the second binder material is present in an amount of about 7 wt% to about 20 wt% of the total dry gain of the first coating of the catalytic coating.

19. An emissions treatment system for treating an exhaust gas stream, the emissions treatment system comprising:

i. an engine that produces an exhaust gas stream; and

a catalyst article according to any one of embodiments 13 to 18 positioned downstream of the engine and in fluid communication with an exhaust stream.

20. The catalyst article of any one of embodiments 13 to 18, wherein the washcoat total mass loss is less than 6%.

21. The binder composition of any one of embodiments 1-8, wherein when the binder composition is part of a washcoat, the washcoat total mass loss is less than 6%.

22. The washcoat slurry of any of embodiments 9-12, wherein a total washcoat mass loss is less than 6% when the slurry is coated on a substrate.

Examples of the invention

Aspects of the present invention are more fully described by the following examples, which are set forth to illustrate certain aspects of the present invention and are not to be construed as limiting the invention.

Tests were conducted to evaluate the effect of different ratios of binder components on the properties of the washcoat composition and the performance of the coatings formed using the washcoat composition. The washcoat composition is prepared with a first binder formed from a plurality of alumina particles having an average particle size of about 78nm and with a second binder formed from a plurality of ceria/zirconia particles having an average particle size of about 28nm and/or zirconia/yttria particles having an average particle size of about 24 nm. That is, the second binder is a plurality of ceria/zirconia particles or a plurality of zirconia/yttria particles, or the second binder is a combination of a plurality of ceria/zirconia particles and a plurality of zirconia/yttria particles. The average particle size of the adhesive component was measured by dynamic light scattering using a Malvern Zetasizer Pro.

For each test sample, the first washcoat composition (used as a base coat) was prepared to have a total solids content of about 2.172g/in formed from binder and catalyst³The slurry of (1). The solids loadings shown in the table below for the first washcoat composition contained both particles having a first relatively larger average particle size and particles having a second relatively smaller average particle size. The second washcoat composition (used as a topcoat) was prepared to have a total solids content of about 1.366g/in formed from the binder and catalyst³The slurry of (1). The second washcoat composition contained a solids loading of 0.025g/in³(second Carrier)1.83 wt.% of the total solids content of the coating) of first binder particles (i.e., having a relatively larger average particle size), but does not contain any second binder particles having a relatively smaller average particle size. The viscosity of the first washcoat composition (used as a primer on a substrate) is also shown in the table below.

The first and second washcoat compositions for each test sample were applied to a flow-through substrate made of cordierite material having a cell density of 600 cells per square inch and having a wall thickness of about 4.3mm by: immersing the flow-through substrate in the slurry to a defined depth; applying a vacuum to draw the slurry up at least part of the length of the substrate into the cells of the flow-through substrate in a direction from the first end of the substrate to the second end of the substrate; removing vacuum; rotating the flow-through substrate 180 °; and applying an air blast through the cells of the flow-through substrate in a direction from the first end of the substrate to the second end of the substrate such that the slurry is coated across substantially the entire length of the substrate. Suitable methods for coating a flow-through substrate are provided in U.S. patent No. 7,521,087, the disclosure of which is incorporated herein by reference. The method involves coating the interior of a hollow substrate with a washcoat composition by: partially submerging an end of a substrate into a vessel containing a bath of coating slurry; and applying a vacuum to the partially submerged substrate at a strength and for a time sufficient to draw the coating slurry from the bath up into the interior of the hollow substrate. In the next step, the substrate is rotated and air is applied to the end of the substrate that has been submerged into the slurry to distribute the washcoat composition therein. The base coat is applied according to the above method using a first washcoat composition and dried before the top coat is applied according to the above method using a second washcoat composition.

Washcoat loss tests were performed on the coated flow-through substrates to evaluate the performance of catalytic coatings containing various ratios of binder. A rigorous multi-step washcoat adhesion test was performed on the catalyst including the binder package. Each catalyst was divided into three sections (top, middle and bottom) and each section was subjected to a thermal shock step, an ultrasonic water bath step and an air blowing step to evaluate the adhesion of the catalyst washcoat under different conditions. Specifically, the catalyst sections were tested after a heating/quenching cycle at about 850 ℃. Washcoat adhesion (WCA) is shown in the table below as washcoat loss, which represents percent washcoat adhesion loss (based on the difference between catalyst segment masses before and after being subjected to the above treatment). A total mass percent loss of less than 6% of the bulk coating under these conditions indicates a robust WCA.

FIG. 8 provides a contour plot showing the viscosity of the first washcoat composition based on the relative loading of the first binder material formed from relatively larger average size particles and the second binder material formed from relatively smaller average size particles. Using a Brookfield viscometer at room temperature for about 300s^-1The shear rate of (c) measures the viscosity. The figure shows that a preferred lower viscosity is achieved using a defined ratio of first binder particles to second binder particles. Fig. 9 provides a contour plot showing percent washcoat loss based on the relative loading of the first binder particle and the second binder particle. The figure shows that a preferred lower washcoat loss is achieved using a defined ratio of first binder particles to second binder particles.

Following the general procedure described above, the following examples were prepared.

The + second binder is a combination of a plurality of ceria/zirconia particles and a plurality of zirconia/yttria particles.

Many modifications and other embodiments of the subject matter of the present disclosure will come to mind to one skilled in the art to which this subject matter pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments described herein and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (19)

1. An adhesive composition, comprising:

a first binder material formed from a plurality of particles having a first average particle size; and

a second binder material formed from a plurality of particles having a second average particle size;

wherein the ratio of the first average particle size to the second average particle size is about 2 or greater.

2. The adhesive composition of claim 1, wherein the first adhesive material and the second adhesive material are independently selected from the group consisting of: alumina-containing materials, silica-containing materials, zirconia-containing materials, ceria-containing materials, lanthanum oxide-containing materials, yttria-containing materials, and combinations thereof.

3. The binder composition of claim 1, wherein the first binder material is an alumina-containing material and the second binder material is a zirconia-containing material.

4. The adhesive composition of claim 1, further comprising a third adhesive material formed from a plurality of particles having a third average particle size, wherein a ratio of the first average particle size to the third average particle size is about 2 or greater.

5. The adhesive composition of claim 1, wherein the first average particle size is from about 50nm to about 1000 nm.

6. The adhesive composition of claim 1, wherein the second average particle size is from about 10nm to about 500 nm.

7. The adhesive composition of claim 1, wherein the first adhesive material and the second adhesive material are present in a concentration ratio of about 0.01 to about 0.5.

8. The binder composition of claim 1, wherein one or both of the first binder material and the second binder material are catalytic.

9. A washcoat slurry comprising:

a liquid medium;

the adhesive composition of any one of claims 1 to 8.

10. The washcoat slurry of claim 9, wherein the binder composition is at about 0.01 to about 1.0g/in³And wherein the washcoat slurry is present in about 300s^-1The viscosity of (a) is about 100cP or less.

11. The washcoat slurry of claim 10, wherein the washcoat slurry is in about 300s^-1The viscosity of (a) is about 50cP or less.

12. The washcoat slurry of claim 9, further comprising a catalyst material.

13. A catalyst article comprising a catalyst substrate having a plurality of channels adapted for gas flow, a wall surface of each channel adhered to a catalytic coating comprising the adhesive composition of any one of claims 1 to 8.

14. The catalyst article of claim 13, wherein the catalytic coating comprises a catalyst material in combination with the binder composition.

15. The catalyst article of claim 13, wherein the catalyst substrate is a honeycomb comprising a wall-flow filter substrate or a flow-through substrate.

16. The catalyst article of claim 13, wherein the catalytic coating is at least about 1.0g/in³Is present on the substrate.

17. The catalyst article of claim 13, wherein the catalyst substrate comprises a first coating layer of the catalytic coating and comprises a second coating layer having a different overall composition that overlies at least a portion of the first coating layer of the catalytic coating.

18. The catalyst article of claim 17, where one or both of the following conditions are met:

the first binder material is present in an amount of about 0.1 wt% to about 5 wt% of the total dry gain of the first coating of the catalytic coating;

the second binder material is present in an amount of about 7 wt% to about 20 wt% of the total dry gain of the first coating of the catalytic coating.

19. An emissions treatment system for treating an exhaust gas stream, the emissions treatment system comprising:

i. an engine that produces an exhaust gas stream; and

a catalyst article according to any one of claims 13 to 18, positioned downstream of the engine and in fluid communication with an exhaust stream.

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